1. Field of the Invention
The present invention relates generally to the measurement of the depth of a recess or pocket and more particularly it relates to a probe instrument used to measure the depth of the gingival sulcus and periodontal pockets.
2. Description of the Prior Art
Chronic periodontal disease is an inflammatory disease typically induced by plaque formation. A consequence of the disease is progressive bone loss around the teeth. The resulting increase in sulcus depths in the gums creates periodontal pockets, which are indicative of the progression of the disease. To diagnose and treat periodontal disease adequately, the depths of the gingival sulcus and any periodontal pockets that exist must be determined accurately.
Pocket depths have been commonly measured by a periodontal probe that has a thin metal tip that is scored with calibration marks. The probe is inserted into the sulcus between a tooth and the gingiva and advanced until resistance is felt, which indicates that the bottom of the pocket has been reached. A depth reading is then obtained by observing visually the calibration mark that is closest to the top of the gingival margin. Six depth readings are taken around each tooth at prescribed locations, as standard practice. Each of the six readings is recorded. Frequently this recording is done by verbal reporting of the depth to an assistant, who writes it by hand on a dental chart.
Clearly, the use of such a conventional periodontal probe is a time-consuming and hence expensive procedure. Moreover, the depths of the periodontal pockets recorded during such a procedure are not always very accurate. Human error results from the need to interpolate between the calibration marks on the probe, as well as from variations in the pressure of the probe against the bottom of the periodontal pocket at the instant that the depth reading is taken. Additional error sometimes arises from the verbal communication of the measured values and the manual writing of those values on the record.
A more recently developed technique is to use a periodontal probe that contains a thin probe of circular cross-section that can be pushed out of a handle and into a sulcus by the operator of the probe. The handle is designed to provide a constant frictional force on the probe, to prevent injury to the gingival tissue.
Another recently developed periodontal probe instrument, invented by Murphy et al, contains a displacement-sensing probe element and a parallel force-sensing probe element in a common handle, together with circuitry for generating electrical signals indicative of the force and the displacement. This invention of a probe instrument is an improvement of that periodontal probe instrument.
The following patents contain descriptions of periodontal probes with a depth measurement structure:
______________________________________ U.S. Pat. No. Dated Patentee ______________________________________ 3,058,225 Oct. 16, 1962 Ward 3,943,914 Mar. 16, 1976 Grenfell et al. 4,203,223 May 20, 1980 Lautenschlager et al. 4,250,895 Feb. 17, 1981 Lees 4,340,069 Jul. 20, 1982 Yeaple 4,665,621 May 19, 1987 Ackerman et al. 4,677,756 Jul. 7, 1987 Simon et al. 4,708,647 Nov. 24, 1987 Pippin et al. 4,791,940 Dec., 1988 Hirschfeld et al. 4,904,184 Feb. 27, 1990 Murphy et al. ______________________________________
In addition, there is a description of a periodontal probe in a paper entitled "Computerized Periodontal Probe with Adjustable Pressure", written by E. Sild et al., which was published on pp. 53-62 of The International Journal of Periodontics and Restorative Dentistry for April, 1987.